/Engine/Source/Runtime/SlateCore/Public/Styling/SlateStyle.h
a FVector2D property.
virtual FVector2D GetVector ( const [FName](API\Runtime\Core\UObject\FName) PropertyName, const ANSICHAR * Specifier, FVector2D DefaultValue, const [ISlateStyle](API\Runtime\SlateCore\Styling\ISlateStyle) * RequestingStyle ) const